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IPM Scouting in Herbaceous Perennials

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Bacterial leaf spot
IPM scouting in herbaceous perennials > bacterial leaf spot
Pathogen: Pseudomonas spp. and Xanthomonas spp.

Hosts include: Astilbe, Chrysanthemum, Delphinium, Echinacea, Heuchera, Hypericum and Rudbeckia.

Symptoms: Disease symptoms include water-soaked lesions on foliage that darken with age. Lesions may be bordered by the leaf venation.

Spread: Bacteria on the plant surface are easily spread to nearby plants by splashing water from rain and irrigation. Asymptomatic plants can serve as a source of inoculum.

Management: Bacterial pathogens can survive and reproduce on the surface of asymptomatic plant tissues. Disease symptoms develop once the pathogen reaches high population levels on the plant surface. Sanitation is especially important. Workers should wash their hands after handling diseased plants. Foliage should not be handled when it is wet. Symptomatic plants should be destroyed. Avoid overhead irrigation or time irrigation to minimize leaf wetness. Succulent tissue is especially susceptible to infection. Most fungicides are not effective against bacteria. Copper-based products are helpful in limiting populations of surface-borne populations of bacterial pathogens.
Bacterial leaf spot on ivy Bacterial leaf spot on Heuchera
Xanthomonas leaf spot of ivy. Note the water-soaked halos around leaf spots. Bacterial leaf spots on Heuchera.
This information was developed from A Pocket Guide for IPM Scouting in Herbaceous Perennials by Jan Byrne and Raymond A. Cloyd. Purchase this in a pocket-sized guide for reference in the orchard from MSU Extension (publication E-2981).
The MSU IPM Program maintains this site as an access point to pest management information at MSU. The IPM Program is administered within the Department of Entomology, fueled by research from the Michigan Agricultural Experiment Station, delivered to citizens through MSU Extension, and proud to be a part of Project GREEEN.
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Updated 8/08/07